Read this a while ago: the space-opera theme of aliens attacking Earth. The defenders fly "space shuttles" armed with rockets (perhaps originally intended for meteor defense). Notably the Earth defenders win because the Earth has a power station in orbit transmitting down to the planet via a microwave beam and the mothership/fleet is tricked to fly into its path. I skipped though it, reading bits and pieces, so I have few details.
Edit: LAK answered it correctly (see later): Armada by Michael Jahn of 1981. Page 207 to 208 in the copy I found details the microwave beam blasting Armada. Not poetry by any means, but it was bugging me. All of your help is very much appreciated and I hope I marked the answer correctly (first time use).